1. Field of the Invention
Embodiments of the present invention generally relate to using electronic lapping guides to set a read sensor's stripe height, or more specifically, to increasing shunt resistance when monitoring the electronic lapping guides.
2. Description of the Related Art
A typical magnetoresistive (MR) read head includes an MR read sensor, which is located between first and second shield layers. When the read sensor is subjected to positive and negative signal fields from tracks on a rotating magnetic disk in a disk drive, the resistance of the read sensor changes. These resistance changes cause potential changes in a sense current flowing through the read sensor, which are processed as playback signals by processing circuitry.
The read sensor has an exterior surface that faces the rotating magnetic disk and is supported on an air bearing from the rotating disk. This exterior surface is referred to as an air bearing surface (ABS). The read sensor has a back edge that is recessed in the read head opposite the air bearing surface. During fabrication, the ABS is defined so that the read sensor has a precise stripe height—i.e., the distance between the ABS and the back edge. This is accomplished by lapping (grinding) a wafer on which the MR head is constructed until the desired stripe height is achieved.
One technique for determining whether the read sensor has the desired stripe height involves transmitting a current through the read sensor and measuring the change in resistance as the ABS is lapped. However, the materials of the read sensor may introduce noise into the current that makes this technique unreliable. Instead, an electrical element called an electronic lapping guide (ELG) may be fabricated on the read head proximate to the read sensor. Moreover, the ELG may be made of similar materials and have similar dimensions as the read sensor. For example, the ELG may be formed in the same photo and subtractive processes as the read sensor to make the elements co-planar. Thus, as the ABS is lapped, the dimensions of the ELG and the read sensor are affected in a similar manner. Moreover, the materials of the ELG may be selected such that a current flowing through the ELG reliably indicates the changing resistance as the lapping process grinds the ABS—i.e., the ELG, when lapped, generates a signal with less noise relative to the read sensor. The resistance of the ELG may be correlated with a particular stripe height. Once the resistance that correlates to the desired stripe height is achieved, the lapping is stopped. Because of the shared physical dimensions of the ELG and the read sensor, a read sensor proximate to the ELG is assumed to have the same stripe height as the ELG.
An ELG may further comprise probe contacts for precise control and measurement of the lapping process. As structures are becoming increasingly smaller, probing the ELG pads becomes problematic as the ELG and transducer pads are present in increasingly reduced dimensions. Due to physical size limitations, bonding of the ELG often inadvertently contacts the component pads. If a read pad is in contact when probing the ELG pad and the read transducer has resistive shunts to the system ground, errors in the ELG measurements may result.
A known solution is to increase the read transducer's shunt resistance. However, the materials used to cause the increase in the resistor shunt layout occupy an extremely large portion of the slider area and are impractical to implement as there is a desire for increasingly smaller devices. Another solution may be to user higher-cost probe connections that support a finer pitch/spacing resolution such that probing both the ELG pad and another pad is not possible. However, this solution is generally more expensive to implement, and thus, generally undesirable.
Therefore, what is needed in the art is a transducer resistor shunt structure for reliable and low cost probing.